A mechanism for removing metallic objects from a moving conveyor belt without stopping it was disclosed by Wilson in U.S. Pat. No. 5,351,802, issued Oct. 4, 1994. In this apparatus, a metal detector, which is positioned upstream of a dumping station, senses the presence of a metallic object such as tramp metal travelling on the belt. A signal from the metal detector then triggers a computer counter. Preprogrammed for compatibility with the speed of the conveyor belt, the counter allows the detected metallic object to move, undisturbed, to a point proximate with the entrance to the dumping station. Upon the metal object""s reaching this entrance, a control unit activates a scraper bladexe2x80x94which is otherwise held above the conveyor belt, and the blade is lowered until it is near or just above the belt. Simultaneously, an array of horizontally disposed idlers, stored beneath the belt, is raised upwardly, flattening it. The idlers are positioned in a pattern such that when they are in contact with the belt, only a portion of it is supported. An unsupported part of the belt to one side of idlers forms a soft spot. With this combination, the blade can be used to direct the metal object, as well as a relatively small amount of the overburden containing it, off of the belt. This mechanism has been put into practice and is working well. However, many of its components must be field installed and customized to each individual conveyor belt.
The primary object of the present invention is to provide an improved mechanism for removing metallic objects from a moving conveyor belt without stopping it, which can be factory assembled, with only a minimum amount of field work being required to install it on a particular conveyor belt.
A further object is to provide a relatively simple mechanism for removing both ferrous and non-ferrous metallic objects from a continuously moving conveyor belt, thereby lowering both factory and installed costs.
A still further object to provide a system which utilizes a scraper blade for removing relatively small quantities of the total flow of bulk materials transported on a conveyor belt, which, under normal operating conditions, is supported in a trough-like configuration.
In accordance with the present invention, there is provided an improved metal removal system, identified herein by the acronym xe2x80x9cMARSxe2x80x9d (for Metal Automated Removal System), for directing one or more metallic objects, as well as a bulk material contaminated with them, off of a moving conveyor belt. In the MARS system, instead of raising an array of idlers in order to flatten the belt, as is taught in U.S. Pat. No. 5,351,802, the scraper blade itself and a pair of press-down feet mounted on the distal ends thereof are used. So that the belt is protected during the flattening process, the press-down feet protrude downwardly a short distance below the lower edge of the scraper blade and each press-down foot, while the belt is supported in its normal trough-like configuration, is disposed above a part of the belt which is situated just inside one of its outer edges. In addition, not only are the press-down feet fabricated of high density plastic but also the lower edge of the scraper blade is covered with a high density rubber guard. Moreover, where the belt is pushed flat by the blade and press-down feet, it slides across a plurality of elongated high density plastic strips which act as bearing surfaces. Disposed generally parallel to the centerline of the conveyor belt, these strips leave those portions of the belt contacted by the press-down feet, as well as an outer edge of the belt proximate with the strips, unsupported. In use, the flattened belt slips beneath the plastic press-down feet and between the rubber guard and the plastic strips while the lowered scraper blade diverts, via a soft spot which forms to one side of the strips, metal-contaminated bulk material away from the belt.
The improved metal removal system also includes a counterweight mounted on the distal ends of support arms for the scraper blade. The counterweight not only allows the scraper blade to be raised more easily than would otherwise be practicable but also it prevents the scraper blade from falling onto the belt during loss of operating air pressure.